Chemical process



Oct. 31, 1944. y B M, FlLBERT l 2,361,465

CHEMICAL Pnocgss Filed Dec. 17, 1941 maar h Patented Oct. l, 1944 UNITED sTA'vrlss .PATENT formes r CHEMICAL PROCESS Bryson M. Filbert, Wooster, Tex., asslgnory to pment Company, a corpo- Standard Oil Develo ration of Delaware' Application December 17, 1941, Serial No. 423,294 6 Claims. '(Cl. 26o-683.4)

, The present invention relates to improvements in the art of synthesizing hydrocarbons and, more particularly, it relates to the alkylation of isoparafns with oleflns in the presence of alkylation catalysts, such as sulfuric acid.

In the conventional practice of alkylating isoparafflns with olefins, the normal procedure involves contacting the isoparafilms) with the oleunder proper conditions of temperature, pressure, and the like, in which zone the solution is contacted with isoparain. Experience has shown that, in order to obtain the. best results, the mola] ratio of isoparaftln to olefin should be such that the isoparaln is in large excess. l s

In its essence, my present invention is a twostage alkylation process, in the ilrststage of which the oleflns to be alkylated are dissolved in sulfuric acid under conditions such that the degradation ofthe olefin is at a minimum, and that the contamination of paraflins present in the olenic feed stock is at a minimum. The solution of olefins and sulfuric acid is then subsequently used for alkylation according to known methods,

One object of my present invention, therefore, is to carry out the alkylation of an isoparaiin with an olefin lnthepresence of sulfuric acid in a two-stage operation, including an absorption stage and an alkylation stage proper, under such conditions that, in the absorption stage, the feed stock containing both paraiiins and olens is treated under conditions such thatv there is a maximum recovery of olens, without degradation, for the process and a minimum4 contamination of the parains with esters and other contaminating material. 1

In the usual two-stage process of alkylating isoparaflinswith oleflns, the olefin charging stock is eected between the extract and the ralnate in the absorption zone, the paralinic ramnate is contaminated with appreciable quantities of dialkyl sulfates. It is an important object of my present invention to remove the alkyl sulfates, principally the dialkyl sulfates, from the paraffins withdrawn from the absorption zone, so the paraflins may be utilizable as a gasoline blending stock or as a charging stock to a thermal polymerization process -or other hydrocarbon reactions, including gas reversion, naphtha reforming in the presence of added butane, andthe like.

My invention will be best understood by reference to the accompanying drawingwhich shows diagrammatically a form and arrangement of apparatus elements in which my'invention may be'carried into practical effect.

I shall now set forth a specific embodiment of my invention and, in so doing, I shall refer to the accompanying drawing in order to providea better understanding thereof, but it is to be understoodl that the precise details I am about to set .stock comprising a liquefied mixture of normally forth do not constitute ventlon.

Referring in detail tothe drawing, a charging a limitation on my ingaseous hydrocarbons containing 15% of normal butylene with substantially no isobutylene, the

yremainder being butane, isobutane, and minor quantities of C3 and Cs hydrocarbons enters the system through line I. 'I'he best feed stock for an operation yof the type I am about to describe is one which is substantially `free of isooleflns.

` I'he charging stock preferably is not at atemperature greater than atmospheric. The feed stock is charged into an absorber 3 where it contacts sulfuric acid-discharged from line 4 into -said absorber, preferably through a system of jets 4or sprays 6, preferably disposed in the upper portion of the absorber. The source of this acid will be hereinafter more fully described and 'identifled. The absorption acid is discharged into y"the absorption zone 3 in such amount:` with reordinarily contains substantial quantities of parains, and the charging vstream containing the olens is usually in the liquid phase. .During the absorption, at least a portion of the sulfuric acid reacts with the oleflns to form alkyl sul.

spect to the olefin entering the absorber that the molal ratio of acid to olefin is approximately 1 to The temperature prevailing in the absorber is approximately 25 F. to,30 F., and the pressure is from aboutlO to 25 iba/sq.' in. gauge. Since the dissolution of oleiins in sulfuric acid, as is well known,v is a phenomenon in which heat is liberated, and since it is necessary' to maintain a temperature within the absorber at a value not greater than about 30 F.,'it is necessarytoprovide means for disposing of the heat released during the dissolving ofthe olenns. I4 proposeto kback to the absorption absorb substantially all of such heat released by vpermitting at least a portion of the paramns to evaporate within the absorber I. It will be understood, of course, that the same result, that is to say, the refrigeration or heat absorption, could be accomplished by external cooling means. In the absorber, as indicated, a substantial quantity of the olefin contenir of the' charging stock is dissolved in the acid and collects in a well or sump Il disposed in the bottom oi the absorber, as

v shown in the drawing. It is pointed out that the quantity of acid-olefin solution or emulsion maintained in the absorber 3 is the minimum amount necessary tov prevent escape of undissolved hydrocarbone as acid extract through line i2.

' ization plant, orthe like, or charged to fractionating equipment in order to `recover any isoparaii'lns present for use in the alkylation system.

Referring again to theabsorber, the unvaporassi,

ized paraiiinic fraction is withdrawn through line 22, and discharged into a vessel Il having disposed-therein a heating coil 28 through which hot water or otherl heating iluid maybe circulated in order to vaporize'thc parailin. The vsp'orized paramos are then withdrawn through line 30 and discharged into line i! for utilization with the paraiiinsin line Il. Since the alkyl sulfatos in the hydrocarbon fed to vaporizer 2t are subject to polymerization and excessive de'- composition ii heated strongly, it is important to maintain the temperature therein below P., lprefersblybelow 301'. Conveniently, the low'temperature invvaporiserft or absorber 3 2l in such manner as to reduce the pressure in these vessels and thereby permit evaporation of the hydrocarbons at the low temperature. -'The paraiiins contained in line 22 have dissolved therein an "appreciable quantity of dlalkyl sultaining the monoand dlalkyl sulfates and this stronger acid would tend to-cause undesirable polymerization if it, alone. were fed into the absorber. A

The extract in line 43 proceeds to the alkylation unit through line Il which, in conjunction with line 45, is a recycle line, and the coniluents of the fresh charge plus the recycle are proportioned in the known manner; the mixed streams are pumped by pump I8 into the alkylator l5, where they are permitted to remain under known conditions for a proper time toeiect the desired "alkylation, The product from the alkylator is withdrawn through line B8 and delivered to-a settling tank 51, from which the crude alkylate is withdrawn through line B8 and delivered to renning equipment to produce the finished product. The bottoms, that is to say, the acid layer,

is withdrawn from the bottom of settling tank El through line 48and recycled to absorber 3 u as previously mentioned. It is` pointed out that, as shown in the drawing and as is well known to those familiar with this art, a portion of the settled acid from settler .51 may be recycled through lines 4B, I9, `4,3 and Il to the alkylator It. It is also pointed out that a portion ofthe acid withdrawn from settler I1 may be discarded through line 82 and be replaced by fresh strong acid introduced through line 66 in order to maintain the acid in the alkylation stageat the desired strength.

A part'of the unreacted isoand normal parailins are evaporated in reactor lli to absorb the heat of reaction and maintain the desired reactor temperature. The vapor-ized hydrocarbons are withdrawnl overheadfrom alkylation reactor 5l through line 10, compressed in pump 1I, and are then recycled, preferably after fraclor both may be obtained'by oporhoting compressor fates. say, about 3% by wt., and amuch less quantity or monoalkyi sulfatos. As previously pointed out, the solubility of dialkyl sulfates in butano or other paraflin hydrocarbons is appreciable and, consequently, after removal of the butano by evaporation from vessel 2l. the -bottoms withdrawn by pump'ii in line l! will be composed substantiaily of the comparatively non-` volatile dialkyl sulfates formerly dissolved in the paramn hydrocarbons. These dialkyl sulfatos are recycled to the absorption tower 3 through line l where they suppress the formation of additional quantities of dialkyl sulfatos from fresh -feed olefins entering the said absorber.

The bottoms from the absorption tower I are withdrawn through line i1, as previously indicated, andthence pumped by pump I! in part tower-through lines l! and l. and the remainder are conducted through line Il to the alkylation sone. It is pointed out at this time, however, that the ratio of bottoms or extract recycled through lines I! and I, to

absorber i, is about ten times the weight oi' the extract which is delivered to the alkylation none. The large proportion of recycled extract to the 'absorber is desirable since the acid returned thrown une u from the alkviauun stage. as win more tulw appear hereinafter, has a higher titratable. acidity than lthe recycled extract contionation to remove normal paraiiins inY apparatus not shown along with extraneous isoparaiiins through isoparaiiin charging line 50,. It is to be understood, of course, that, in the preceding description, I do not claim that the allrylationI stagev proper is anything other than the conventional method of carrying out this particular portion of my process. The invention resides.

as stated, in the first, or absorption, stage of the process, particularly with regard to the method of suppressing the formation of additional quantities of dialkyl sulfate from the fresh olefin feed entering the system.

rt wm be understood thai-not only may raikylate isobutane with normal butylene. but I may' `also alkylate other normally gaseous or normally liquidA isoparamns with other normally gaseous and/or normallyliquid olefins. y

Many modifications of my invention will readily suggest themselves to those who are familiar with this art without departing from the spirit thereof.

The present invention having been thus described and illustrated, what is claimed as new and 'useful and is desired to be secured by Letters Patent is: v

1.4 In a two-stage alkylation process, including an olennabsorption'stage and an alkylation stage proper, the improvement which comprises charging to the first stage a liqueiledf-charging stock containing olenns for alkylation and paramos, contacting said olenns with concentrated sulfuric acid whereby the volefin contentof the charging stock is substantially completely reacted with the sulfuric acid to form dialkyl suliates and monoalkyl sulfates, withdrawing Vthe monoalkyl sulfates as bottoms from the absorption'zone, and withdrawing dialkyl sulfates as the side eut trom" the said absorption zone dissolved in paramn hydrocarbons, separating the paramn hydrocarbons from the diaikyl sulfates, and returning the separated dialkyl sulfates to the absorption zone to suppress further formation of the' same.

2. The process set forth. in claim 1 in which the heat liberated by the reaction between the sulfuric acid and the olens is substantially completely absorbed by permitting at least a portion of the paraln hydrocarbons to evaporate in the absorption zone.

3. The process set forth in claim 1 in which somos 3 4.- The process set forth in claim 1 in which a substantial portion of `the monoalkyl sulfates V of the absorption mne in the absorption is carried out at a temperature i not higher thanabout v30 F.

withdrawn as bottoms from the absorption'zone is recycled to the said .absorption zone to diluteA the acid concentration therein. and to prevent ldegradation of theolen.

5. The process set forth in claim 1 in which, in order to provide intimate contact between acid and olefin hydrocarbons in the absorption zone. the said acid is discharged into the upper portion the form' of droplets.

6. The process set forth in claim 1 in which the absorption is carried out countercmrently.

BRYSON M. FILBERT. 

